The Care of Kimberly Queen Ferns

If you're looking for a plant that makes a bold yet graceful statement, a fern called 'Kimberly Queen' (Nephrolepis obliterata) certainly fits the bill. Also called sword fern because of its straight, narrow upright fronds, it's an Australian native that's about 3 feet tall and 4 feet wide when mature. It's an easy-to-grow plant that thrives outdoors or as a houseplant, needing only a bit of special attention its first season and basic care to grow well.

This fern is naturally fast-growing, doing well outdoors year-round in U.S. Department of Agriculture plant hardiness zones 9 through 11. In the garden, it appreciates some shade, especially during the hot afternoon hours, but can also tolerate some sun during the morning when the air is cool. An ideal garden spot is under the canopy of tall trees that provide shifting shade in the afternoon hours, or on a deck or patio near a roof overhang that provides some afternoon shade.

If you grow a 'Kimberly Queen' fern indoors, it prefers medium light, such as near a lightly curtained south- or west-facing window. It can also thrive in an uncurtained east window, where it gets a bit of direct morning sun.

Like most ferns, a 'Kimberly Queen' needs regular moisture, with soil that never dries out. Water the plant whenever the soil's surface feels slightly dry to your fingertip. Whether in the ground or container-grown, adequate moisture is especially important during the plant's first growing season, when it needs to develop a widely growing root system to support good growth for subsequent years.

It's also important for the fern's soil to drain well so fungal organisms don't grow in the soil and damage its roots. Only use a container with at least one drainage hole, and never leave the pot in a water-filled saucer, which promotes soggy soil.

LIke most ferns, a 'Kimberly Queen' fern grows best when fertilized monthly when it's actively growing, generally from spring until early fall. Whether grown indoors or in the garden, use a balanced, water-soluble fertilizer such as a 20-20-20 formula that's diluted half-strength, usually 1/4 teaspoon per gallon of water, but check the product label for additional directions. Avoid over-fertilizing, which might cause the fronds to dry and turn brown, and withhold fertilizer from mid-fall through winter, to give the plant a rest.

A 'Kimberly Queen' fern doesn't need pruning, with naturally attractive fronds that stay green throughout the growing season. But during winter, some of the older fronds may die back on a houseplant, and outdoors in cooler parts of its range, the top growth might shrivel and become partially or totally dry. In either case, when spring arrives and you see new growth, cut off any dry, brown fronds with sharp shears, disinfecting the blades by wiping them in rubbing alcohol between cuts to prevent spreading disease.

If you grow this fern as a houseplant or overwinter in indoors, raise the humidity in the plant's vicinity to help it do well in dry indoor air. Either use a humidifier to raise the air's moisture content or keep the plant on a pebble-filled tray containing water at a level just below the tops of the pebbles.

A 'Kimberly Queen' fern is usually free of plant diseases when grown in well-drained soil that's never allowed to remain soggy. But several pests can infest the plant, including mealybugs, which are fluffy and white, and feed on the fronds. Control these by touching each one with a cotton swab that's been dipped in rubbing alcohol. Other possible pests include spider mites, which aren't visible but leave webs on fronds and suck the plant's juices, damaging its foliage. These are best destroyed by spraying the fern with insecticidal soap diluted at a rate of 5 tablespoons per gallon of water. Repeat the spray every two weeks, as needed.